Chem Quiz Iv

Front 1

land area is __% of total SA of earth

Back 1

29%

Front 2

how does reactivity of solid materials vary with size?

Back 2

smaller particles = more SA = more reactive than larger particles

Front 3

rocks and soil referred to as ___________ (outer __km of crust)

Back 3

lithosphere
40

Front 4

rocks can be either a single ________ or a(n) _________ (with definitive crystal structure)

Back 4

mineral
aggregate

Front 5

what is an evaporite? where would you find one?

Back 5

a mineral formed by being precipitated out of solution
found in dry places, or else they would dissolve

Front 6

__% of soil volume is air

Back 6

35

Front 7

in what 3 ways to soil properties vary?

Back 7

horizontally, vertically and over time

Front 8

clays (AKA as _____________) are natural water barriers and so are used as what?

Back 8

aluminosilicates
landfill liners

Front 9

what shape of structure do clays form in the soil?

Back 9

sheet-like

Front 10

what are the 2 layers of kaolinite clay?

Back 10

Si-O and Al-O

Front 11

in the structure of the clay montmorillonite, there is a sheet of ________ sandwiched between 2 ________ sheets. this creates a lot of _______ charge, mostly located in the (interior/exterior) layer. this creates a large what? why? it also means that the clay can bind ____, causing it to swell.

Back 11

aluminum, silica
negative, interior
creates a large cation exchange capacity because the cations are held loosely to the surface and so are exchangeable.
water

Front 12

2 main reasons for studying soils

Back 12

1. it's the principal growth medium
2. soils play major roles in global C, P, N, and S cycles

Front 13

complex processes by which rocks on earth’s surface are transformed into soils are collectively known as ________

Back 13

weathering

Front 14

what are the 3 chemical reactions of weathering?

Back 14

hydrolysis
complexation
oxidation/reduction

Front 15

what are the "agents of weathering" in hydrolysis reactions?

Back 15

H3O+ and H2O

Front 16

what process allows Fe3+ and Al3+ to be mobile/soluble in soils? how?

Back 16

complexation - formation of soluble organic COMPLEXES from soil organic matter

Front 17

explain the redox reactions of soil formation

Back 17

primary minerals that contain elements in low oxidation states are exposed to the atmosphere -> oxid state increases -> minerals lose or gain other elements to gain neutrality ==> formation of secondary minerals

Front 18

organic matter makes up _ to _% weight of soil mass and plays a significant role in many _______/________ processes.

Back 18

1 to 5%
physical / chemical

Front 19

what is a primary source of SOM?

Back 19

plant tissue in various stages of decay

Front 20

important contributor to the organic fraction of soil is ___________

Back 20

microorganisms (bacteria, fungi, actinomycetes, protozoa)

Front 21

coatings of humic matter on oxide surfaces can INHIBIT what? what does this mean for the mobility of them?

Back 21

the adsorption of metal ions
mobility of metal ions is greater in soils with UNCOATED minerals

Front 22

_________ _____ hold water in micropores between and inside soil particles

Back 22

capillary forces

Front 23

what are 4 functions of soil pores depending on their size (from largest to smallest pores)

Back 23

transmission - air and water
storage - of water
residual - for ion retention/diffusion
bonding - between soil particles

Front 24

a complete description of environmental reactions of soil must involve what?

Back 24

all three phases of soil

Front 25

how do soil horizons form?

Back 25

rainwater percolating thru the soil carrying soluble and colloidal materials lower into soil

Front 26

what are the soil size categories and their pros/cons?

Back 26

clay - poor drainage and aeration; good nutrients and water retention
silt - middle
sand - poor nutrients and water retention; good drainage and aeration

Front 27

2 examples of clay minerals

Back 27

kaolinite
montmorillonite

Front 28

clay minerals, org matter, primary minerals, and Fe & Al hydroxides all have what in common?

Back 28

they have a large SA = good ion exchange + adsorption = retain nutrients

Front 29

what does soil texture mean?
what is a desirable soil texture?

Back 29

defines soil by the proportion of different sized particles (clay, silt, sand)
35% clay, 30% silt, 35% sand

Front 30

permeability = hydraulic conductivity = what in a soil?

Back 30

measure of soil's ability to conduct water flow (high permeability = rapid water transfer)

Front 31

if a soil has low permeability the soil can become _________, which decreases ___ causing _________ conditions

Back 31

waterlogged (saturated)
pE
anaerobic

Front 32

why is a measure of total elements in a soil not very useful?

Back 32

doesn't indicate if elements are in mineral formed or adsorbed

Front 33

polysaccharides, cellulose, hemicellulose, and pectin are some materials that make up what chemical property of soil?

Back 33

the non-humic material or org matter

Front 34

what are the 4 most important cations?

Back 34

Ca2+ > Mg2+ > K+ > Na+ (and H3O+)

Front 35

under acidic conditions a large portion of cation exchange sites occupied by what? what are 2 consequences?

Back 35

H3O+
1. less nutrients can bind
2. reduced ability neutralize additional acidity

Front 36

how do you calculate BASE SATURATION?

Back 36

(# of exchange sites occupied by Ca2+ Mg2+ K+ Na+) / (total # of exchange sites) X100

Front 37

soils with low CEC and/or base saturation are susceptible to what

Back 37

acidification

Front 38

what are the relative pH's of soils with carbonate minerals (dolomite) vs. HM?

Back 38

alkaline vs. acidic

Front 39

why do flooded soils tend to have higher pH than upland soils?

Back 39

flooded soils are reducing; reducing is gain of electrons, which needs + ions to balance it - H3O+ is consumed so pH rises!

Front 40

what is a big problem in the corn belt?

Back 40

erosion

Front 41

extent of nutrient leaching is determine d by:
flux of _____
soil ______ and
nature of ______ ______

Back 41

water
texture
plant cover

Front 42

how is the downward movement of nutrients thru the soil inhibited geochemically and biologically?

Back 42

geochem - CEC
biol - plant uptake

Front 43

soils with high CEC hold _____ and prevent _____

Back 43

cations
leaching

Front 44

2 ways soils neutralize acid

Back 44

carbonate minerals (if present)
cation exchange

Front 45

CEC + base saturation = a measure of the ________ capacity of soil

Back 45

BUFFERING (?)

Front 46

when there is limited precipitation and high rates of evaporation, ____ accumulate near soil surface

Back 46

salts

Front 47

in what pH range are metals retained in the soil? what happens if the pH falls?

Back 47

7-8
leaching velocity increases and metals are transported to ground water

Front 48

colloid represent the chemistry of the interface between what and what?

Back 48

solid and liquid phase

Front 49

depending on their diameter, materials in the natural aqueous system are classified as one of 3 things - what are they?

Back 49

soluble (smallest)
colloidal
precipitated (largest)

Front 50

in acidic solutions the surface of a colloid is _______, and in basic solution it is _________

Back 50

protonated (+)
deprotonated (-)

Front 51

in humic acid the deprotonation of _____ groups results in negative charge -> surface charge depends on the __ of ________

Back 51

carboxyl
pH of solution

Front 52

what is pH0?

Back 52

ZERO POINT OF CHARGE
pH at which surface + and - charges on a colloid balance

Front 53

when pH of solution < pH0 of colloid = the surface is ______ = net ______ surface charge = ______ are adsorbed
and vice versa

Back 53

protonated
positive
anions

Front 54

the lower the pH0 value is, the more likely the colloid is to possess a ________ surface charge

Back 54

NEGATIVE
(cuz its more like that pH > pH0)

Front 55

what is the electrical double layer?

Back 55

colloid = negative, attracts cations
cations attract anions

Front 56

how do colloids travel to the ocean? what happens when they get there?

Back 56

they remain suspended in solution (stabilized) because of the electrical double layer on small particles that repel each other - once they get there the high [electrolyte] causes them to destabilize, stick together and settle

Front 57

how does the thickness of the electrical double layer change in freshwater vs. ocean?

Back 57

freshwater = large = particles repel one another
ocean = thin = sedimentation

Front 58

cations are retained on the surfaces of negatively charge colloids by _________ __________

Back 58

SPECIFIC ADSORPTION

Front 59

what is CMC and what happens ABOVE it?

Back 59

critical micelle concentration
detergent molecules aggregate into micelles

Front 60

what does the hydrophobic interior of a micelle do that makes it useful?

Back 60

solubilizes oil, grease and dirt and removes them from things (clothing)

Front 61

what happens to a micelle if there is too much Mg2+ and Ca2+? how can you prevent this?

Back 61

polar heads of micelles interact with Mg and Ca causing them precipitate
prevented by adding chelating agents that bind Mg and Ca

Front 62

what is STP and what does it do? why is it bad and what is an alternative?

Back 62

STP = chelating agent - holds Ca and Mg in its center to get rid of hard water
bad = results in eutrophication
alternative = zeolithes

Front 63

what is sodium iminodisuccinate (IDS)?

Back 63

a green chelating agent - biodegradable and non-toxic

Front 64

metals and metalloids make up __% of the periodic table, are found in the earth's crust and as ____/______ in the hydrosphere

Back 64

75
ions/complexes

Front 65

metals and metalloids can exist in an aqueous environments in 3 forms
- ________
- complexes with inorganic _______
- complexes with _______ molecules

Back 65

- aquocomplexes
- ligands
- organic

Front 66

why are uncharged molecules hard to remove from water?

Back 66

they don't stick to anything

Front 67

________ is the simplest form in which metal can exist in water

Back 67

aquo-complex

Front 68

there is an inverse relation relation between the radius of an ion and its radius when it is ________. why?

Back 68

hydrated!
smaller ions are huge when hydrated
because of charge density

Front 69

H2O surrounding metal ions with a single positive charge exist exclusively in ____________ form (pH 0-14)

Back 69

PROTONATED

Front 70

if Z^2/r ratio is large, then _________ is important (Be2+, Al3+, Fe3+) and it's more likely that an _____ bond will form to make complexes

Back 70

deprotonation
IONIC

Front 71

Fe(III) extremely insoluble in water but solubility greatly enhanced if ______ are present that form a stable complex (e.g.humicacid)

Back 71

ligands

Front 72

HM functional groups are ______ charged, so they can act as a ligand in forming complexes with metal ions

Back 72

negatively

Front 73

what was the silent global change?

Back 73

copper contamination caused impaired chemosensation for aquatic animals

Front 74

4 global Hg sources

Back 74

- coal fired power plants
- low tech gold/silver mining
- smelting
- waste combustion

Front 75

70-100% of the Hg in fish is in what form? due to what process?

Back 75

CH3Hg+
biomethylation

Front 76

what is biomethylation
where does it happen?
what properties does it change?

Back 76

when CH3's are attached to a metal/metalloid
happens by microbes/animals/fungi, etc.
changes solubility in water, octanol/water distribution coefficient (bioaccumulation)

Front 77

what is minamata disease from?

Back 77

inorganic Hg was biomethylated to methylmercury by microorganisms in the sediment